What's killing Spruce and Pine trees in Utah?



After more than five years of drought, some of Utah’s native trees are suffering

from prolonged stress. Dry soil in the spring and fall when supplemental irrigation is

typically absent is especially stressful to trees.

In addition, a native group of bark beetles called Ips beetles are attacking spruce

and pine trees in ornamental landscape settings (parks, cemeteries and yards) and nursery

plantings. Native pinyon pines on dry sites are also at risk for infestation by Ips.

Consider the following information to prepare for the upcoming growing season.

* Ips bark beetles are attracted to trees that are under stress. Adult beetles attack in large groups to overcome natural defenses of the trees, such as sap or pitch production. Ips bark beetles live in forested areas of the state, primarily as secondary invaders of trees that are injured and dying from other causes. Now they are beginning to behave as primary invaders, however, killing pinyon pines on dry sites in their native habitat as well as stressed spruce and pine trees, such as those that are inadequately irrigated deep into the root zone, too closely planted, on a poor planting site or stressed from other pests.

* Adult Ips beetles attack spruce and pine trees from spring through fall, entering smaller diameter limbs at the tops first. They can move down the trunk within several months, killing the tree. Other trees nearby are especially at risk of attack. Adults feed in the conductive tissues of the cambium just under the bark creating their characteristic tunnels or galleries. They disrupt the transport of nutrients and water throughout the tree. Life cycles of Ips beetles require six to eight weeks, so up to five generations can occur in a season.

* The most helpful strategy to prevent attack by bark beetles is to avoid stressing trees. Maintain tree vigor and health by watering deeply two to four inches every two to four weeks when soil moisture is depleted from spring through fall. Select a suitable planting site, avoiding dry sites with excessive sand or gravel. Also avoid tree injuries or infestation by other pests.

* Promptly remove trees heavily infested with Ips beetles and dispose of infested wood or treat the wood. To do this, remove all the bark, chip and dry thoroughly and burn it or completely cover it with a clear plastic tarp to generate lethal temperatures. You can protect uninfested trees or lightly infested trees by applying a registered insecticide to the entire trunk or bole. This may require a professional applicator with equipment to reach the tops of tall trees. A drenching spray applied to run-off is necessary to soak cracks and crevices of tree bark. Recommended insecticides are carbaryl (Sevin) and permethrin. The best times to treat are from late April to early May or late September to October when more synchronized populations of adult beetles are flying to new trees.

For more information, refer to two fact sheets on spruce and pine Ips on the Utah Division of Forestry, Fire and State Lands website: http://www.ffsl.utah.gov/id.php.

Posted on 5 Jan 2004

Diane Alston
Hort-Entomologist Specialist

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